Semiconductor integrated circuit (IC) chips are widely used in consumer electronics, telecommunications, and computer systems such as personal computers (PCs). A wide variety of semiconductor chips are made, including analog, system-on-a-chip, microprocessor, controllers, and memory. Perhaps the most widely made are dynamic random-access memory (DRAM) chips. DRAM memory chips are often mounted on small, removable memory modules. Older single-inline memory modules (SIMMs) have been replaced with dual-inline memory modules (DIMMs), 184-pin RIMMs (Rambus inline memory modules) and 184-pin DDR (double data rate) DIMMs. New kinds of memory modules continue to be introduced.
The memory industry is quite cost sensitive. Testing costs are significant, especially for higher-density chips and modules. Specialized, high-speed electronic test equipment is expensive, and the greater number of memory cells on high-speed memory chips increases the time spent on the tester, increasing test costs.
Rather than use an expensive general-purpose I.C. tester, inexpensive testers based on PC motherboards have been developed for memory modules. These motherboard-based testers cost only about $10K yet can replace a quarter-million-dollar I.C. tester when testing memory modules. The memory module to be tested is inserted into a test socket on a test adapter board (daughter card) mounted on the back-side of the motherboard. See “Connector Assembly for Testing Memory Modules from the Solder-Side of a PC Motherboard with Forced Hot Air”, U.S. Ser. No. 09/702,017, now U.S. Pat. No. 6,357,023.
DRAM chips are first packaged and tested individually on test equipment such as automated test equipment (ATE) and then soldered to memory module. Then the memory module is tested on a module tester. Robotic testers that use many PC motherboards for memory modules have been developed by the current inventor. See Co et al., “Automated Multi-PC-Motherboard Memory-Module Test System with Robotic Handler and In-Transit Visual Inspection”, U.S. Pat. No. 6,415,397.
While a variety of chip testers exist, further improvements are desirable. Higher throughput systems are desirable. However, simply increasing the number of test sockets may increase delays as robotic arms must travel longer distances. Adding more robotic arms can result in collisions among robotic arms, or in delays while one robotic arm waits for another robotic arm to get out of the way.
What is desired is a robotic tester for testing integrated circuit (IC) chips. A tester with multiple robotic arms is desired to increase test throughput. A tester with chip-tray buffers that move among roaming areas of each robotic arm is desirable.